Strongly acidic ion-exchange resins may replace mineral acids such as sulfuric acid and hydrochloric acid in catalyzing reactions, as for example condensation reactions. The use of the solid, acidic materials permits easier separation of the desired product from the catalyst in the reaction mixture, decreases equipment corrosion and complexity, and increased product purity. The use of the strongly acidic ion-exchange resins for catalyzing reactions is disclosed broadly in U.S. Pat. No. 3,037,052 to Bortnick, and the use of strongly acidic ion-exchange resins, prepared by sulfonating copolymers of styrene and polyethylenically unsaturated aromatic crosslinking monomers, as catalysts for the condensation of phenols with ketones or aldehydes to produce bisphenols, is disclosed in U.S. Pat. Nos. 3,153,001 to Apel et al., 3,172,916 to Wagner, 3,634,341 to Gammill et al., 4,590,303 and 4,391,997 to Mendiratta, 4,424,283 to Faler et al. and others. Of particular interest is their use to catalyze the condensation of phenol with acetone to produce Bisphenol-A (para, para'-isopropylidenediphenol), which is useful as a raw material for producing polycarbonates and epoxy resins.
The copolymer beads used to make ion-exchange resins are preferably spherical beads, and a uniform bead size throughout a particular batch of copolymer is desirable because it produces uniform, predictable hydraulic properties, such as flow rate and pressure drop, for a bed of the resin in a reaction vessel. Suspension polymerization, in which water-insoluble monomers are suspended and polymerized as discrete droplets in an aqueous medium, inherently produces beads that are generally spherical. The size of the beads depends upon the size of the monomer droplets that form, and various techniques are used to control the diameter and uniformity of the droplets. Additives are used in the aqueous phase to help control droplet size by varying the interfacial tension between the monomer and the aqueous medium; they also are used to limit the growth of coalescence of the monomer droplets. The intensity of agitation is also varied to help control the droplet size. Suspension polymerization has been used for over half a century to produce the copolymer intermediates for ion-exchange resins, as is disclosed for example by Boyer in U.S. Pat. No. 2,500,149, One technique that has been used to increase the uniformity of the droplet size is jetting a stream of monomer through an accurately sized orifice into the aqueous phase, as for example the process disclosed by Koestler et al. in U.S. Pat. No. 3,922,255.